量子電腦 - 中研院物理研究所
量子電腦 - 中研院物理研究所
量子電腦 - 中研院物理研究所
You also want an ePaper? Increase the reach of your titles
YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.
Superposition and entanglement<br />
• Superposition<br />
a<br />
0 + b 1<br />
i 10<br />
t<br />
a 0 + b 1 e − ω<br />
a 0 +<br />
b 1 e<br />
−<br />
i<br />
ω t + i<br />
ϕ<br />
− 10<br />
• Entanglement (composite systems)<br />
1 1<br />
Separable: ϕ = 0 0 + 0 1 = 0 ⊗ 0 + 1<br />
2 2<br />
1<br />
Entangled : Ψ = ( 0 1 − 1 0 ) ≠ ψ ⊗ φ<br />
A B A B A B<br />
2<br />
• Partial trace (composite systems)<br />
1<br />
TrA<br />
⎡⎣<br />
ϕ ϕ ⎤ ⎦ = ( 0 + 1 )( 0 + 1 ) pure state<br />
B<br />
2<br />
1<br />
TrA<br />
⎡⎣<br />
Ψ Ψ ⎤ ⎦ = ( 0 0 + 1 1 ) mixed state<br />
B<br />
2<br />
( ) ( )<br />
A B A B A B B